The environment, social interaction, and behavior play an important role in the control of ovarian function in the young mature rat. The research proposed in this grant constitutes an integrated analysis of the effects of these factors on reproductive senescence. This research has three primary goals. 1) A description of the changes in physiological and behavioral components of the female rat's reproductive cycle during aging under seminatural conditions. 2) An examination of the control of the rate and/or reversibility of these changes both longitudinally and acutely. 3) This will elucidate the role of social interaction, sexual behavior, circadian activity rhythms and the lighting environment on ovarian aging in this species. Additionally, the role of these factors will serve as a more general model for the reciprocal interactions of behavior and physiology in the aging of reproductive function and will elucidate their integration in the younger animal as well.